XRT7250 datasheet(216/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

197

When the µP reads these registers, it will read in the

number of parity-bit errors that have been detected by

the Receive DS3 Framer block, since the last time

these registers were read. These registers are reset

upon read.

NOTE: When the Framing with Parity option is selected, the

Receive DS3 Framer block will declared an OOF condition

if P-bit errors were detected in two out of 5 consecutive DS3

M-frames.

3.3.2.6.2 CP-Bit Checking/Options

CP-bits are very similar to P-bits except for the follow-

ing.

1. CP-bits are used to permit performance monitor-

ing over an entire DS3 path (e.g., from the source

terminal) through any number of mid-network ter-

minals to the sink terminal).

2. P-bits are used to permit performance monitoring

of a DS3 data stream, as it is transmitted from

one terminal to an adjacent terminal.

How CP-Bits are Processed

The following section describes how the CP-bits are

processed at three locations.

• The Source Terminal Equipment

• The Mid-Network Terminal Equipment

• The Sink Terminal Equipment

Figure_62 presents a simple illustration of the loca-

tions of these three types of Terminal Equipment,

within the Wide-Area Network.

NOTE: The use of the terms Source and Sink Terminal

Equipment are used to simplify this discussion of CP-Bit

Processing. In reality, the Source Terminal Equipment (in

Figure_62) will also function as the Sink Terminal Equip-

ment (for DS3 traffic traveling in the opposite direction).

Likewise, the Sink Terminal Equipment (in Figure_62) will

also function as the Source Terminal Equipment.

Processing at the Source Terminal Equipment

PMON PARITY ERROR EVENT COUNT REGISTER - LSB (ADDRESS = 0X55)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT2BIT 1BIT 0

Parity Error Count - "Low" Byte

0000

000

FIGURE 82. A SIMPLE ILLUSTRATION OF THE LOCATIONS OF THE SOURCE, MID-NETWORK AND SINK TERMINAL

EQUIPMENT (FOR CP-BIT PROCESSING)

Source

Terminal

Equipment

Source

Terminal

Equipment

Sink

Terminal

Equipment

Sink

Terminal

Equipment

Mid-Network

Terminal

Equipment

Mid-Network

Terminal

Equipment

The Wide Area Network

Customer

Premises

Equipment

Customer

Premises

Equipment

Customer

Premises

Equipment

Customer

Premises

Equipment

XRT7250 Datasheet(PDF) 216 Page - Exar Corporation

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